﻿<%@   page contentType="image/jpeg"  
  import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" pageEncoding="utf-8"  %>   
  <%!   
  Color   getRandColor(int   fc,int   bc){//给定范围获得随机颜色   
                  Random   random   =   new   Random();   
                  if(fc>255)   fc=255;   
                  if(bc>255)   bc=255;   
                  int   r=fc+random.nextInt(bc-fc);   
                  int   g=fc+random.nextInt(bc-fc);   
                  int   b=fc+random.nextInt(bc-fc);   
                  return   new   Color(r,g,b);   
                  }   
  %>   
  <%   
    out.clear(); 
    out=pageContext.pushBody();
  //设置页面不缓存   
  response.setHeader("Pragma","No-cache");   
  response.setHeader("Cache-Control","no-cache");   
  response.setDateHeader("Expires",   0);   
    
  //   在内存中创建图象   
  int   width=60,   height=20;   
  BufferedImage   image   =   new   BufferedImage(width,   height,   BufferedImage.TYPE_INT_RGB);   
    
  //   获取图形上下文   
  Graphics   g   =   image.getGraphics();   
    
  //生成随机类   
  Random   random   =   new   Random();   
    
  //   设定背景色   
  g.setColor(getRandColor(200,250));   
  g.fillRect(0,   0,   width,   height);   
    
  //设定字体   
  g.setFont(new   Font("Comic   Sans   MS",Font.PLAIN,20));   
    
  //画边框   
  //g.setColor(new   Color());   
  //g.drawRect(0,0,width-1,height-1);   
    
  //   随机产生155条干扰线，使图象中的认证码不易被其它程序探测到   
  g.setColor(getRandColor(160,200));   
  for   (int   i=0;i<155;i++)   
  {   
    int   x   =   random.nextInt(width);   
    int   y   =   random.nextInt(height);   
                  int   xl   =   random.nextInt(12);   
                  int   yl   =   random.nextInt(12);   
    g.drawLine(x,y,x+xl,y+yl);   
  }   
    
  //   取随机产生的认证码(4位数字)   
  String   sRand="";   
  for   (int   i=0;i<4;i++){   
          String   rand=String.valueOf(random.nextInt(10));   
          sRand+=rand;   
          //   将认证码显示到图象中   
          g.setColor(new   Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));   
  //调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成   
          g.drawString(rand,13*i+6,16);   
  }   
    
  //   将认证码存入SESSION   
  session.setAttribute("rand",sRand);   
    
  //   图象生效   
  g.dispose();   
    
  //   输出图象到页面   
  ImageIO.write(image,   "JPEG",   response.getOutputStream());   
  %>